If you have a crave for swimming and water sports, but want to take a ride at your own pace then you should jump on board a campervan and take one or two months off to explore the east coast of Australia. You can take this road trip either from September to November or from February to April or May. From December to March it rains a lot in Cairns and unless you have a specific desire to hang under the canopy while the one flood replaces the next flood you should avoid this season.
Australia's East Coast road trip route suggestion
Sydney - Byron Bay - Gold Coast - Brisbane - Fraser Island - Kroombit - Rockhampton - Airlie Beach - Whitsundays Island - Cairns